1. Field of the Invention
The present invention relates to a battery voltage measuring device which detects the battery voltage in a power source device formed by connecting a plurality of secondary batteries in series, and in particular, relates to a battery voltage measuring device which quickly detects a breakage of the signal line when a signal line for voltage measurement has been broken.
2. Background Art
Conventionally, hybrid vehicles equipped with an electrical motor in addition to an engine as the drive source for driving the vehicle are known.
One type of control (mode) of these hybrid vehicles is the parallel hybrid vehicle that supplements the output of the engine using an electric motor. In this parallel hybrid vehicle, various types of control are carried out. For example, during acceleration, the electrical motor assists the output of the engine, and during deceleration, the battery is charged by deceleration regeneration. Thereby, the state of charge of the battery (that is, the remaining charge of the battery) can be maintained, while at the same time fulfilling the needs of the driver. In addition, because high voltages are required, this battery is formed by connecting a plurality of battery cells in series.
Conventionally, a battery is formed by connecting a plurality of modules in series, and each module is formed by connecting a plurality of cells in series. In the voltage detection of the battery, voltage sensors are attached to each modules and the voltage of each module is detected by respective voltage sensors. In addition, a noise filter formed by a resistors and a capacitor is interposed between each module and each sensor, and these noise filters eliminate the unnecessary noise component from the voltage signal from the battery voltage sent through the signal line. Thereby, a higher precision voltage detection is possible because an averaged voltage is input into the voltage sensor.
However, in the case of using noise filters formed by resistors and a capacitor as described above in a battery voltage measuring device, the problem arises that when a breakage occurs in the voltage measuring line, in the voltage sensor of the broken voltage measuring line, the voltage of the module is divided by the capacitor of the noise filter, and thus accurate detection of the voltage of the module is not possible.
In addition, the other problem arises that the voltage value of the module detected by the voltage sensor does not differ very much from the normal voltage value and thus a breakage occurring in the voltage measuring line cannot be detected.
As described above, in the case that breakage or other failures occur in the signal line, the detected voltage of the module on the broken signal line is different from the actual value, and accurate detection of the module voltage becomes impossible. Because of this, it becomes very important to immediately detect the breakage of this signal line and to take fail-safe actions.